Purification of cotton linters



50 found to be more eflectivethan individual comsired exampleby distillafim in Patented July 28, 1936 i UNITED STATES PATEN OFFICE- PUBIFIOATION F COTTON LINTERS A l Elmer K. Bolton, Wilmington, DeL, assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application October 1, 1934,

Serial No. 746,473

1 Claim. (CI. 92-13) This invention relates to an improved process pose for which the purified cellulose is to be used, for the purification of cotton linters. viscosity desired in the cellulose, etc. After the long staple fibers, which are used in The following examples are illustrative. of the the textile industry, are removed. from cotton method of practicing my invention: 5 seeds by. the ginning operation there remain E k clinging to the seeds shorter fibers which-may in camp turn be s pa ated y p ss th s s between Five hundred grams of crude second cut cotghs rgg ig d8 E31 z E i 1 ton linters were placed ,in an autoclave and cove 1 remove n 3 e erm ered by 5000 grams ofa 2'7 caustic soda solu- I0 linters, are mainly cellulose and when freed from m eontaining 2 5 grams sulfate of ormal 10 f r i n mpuriti s, su h as seed hull parti s. dodecyl alcohol. It was noted at this point that oils, a es, and grease, serve as'a bas raw 1113- the crude linters we e wet almost instantly by term] in the manufacture of m y cellulose the caustic solution although a caustic solution livatives and Products prepared ther fr n of similar strength containing no wetting agent aon .Theauocave usc arge wascos an ea-. cotton linters is by digestion of the same with ed to 160 C. and maintained at this temperature solutions of caustic soda, generally under presfor ix hours, the pressure throughout beingsureabout 80 pounds per square inch. At the end of 20 This invention has as an object an improvethis period the autoclave was cooled, emptied, 20 ment in the penetrative power of dilute caustic and t digested otto washed free of alkali soda solutions into crude cotton linters. Anothblack ljqubr, Th cotton was next bleached in a er object of this invention is an improvement in 3% slurry using 04% (ba ed on dry weight of he eflicl cy of he digestion process by mean cellulose) of chlorine in the form of calcium hyof which cotton linters are purified fr pochlorite. The resulting bleached product was 25 cellulosicvmaterials such as seed hull particles, possessed of a, high white color which was defitiitidiittiiiitfii? ti t; it" 2? is s'5 if"i a i? an P 1119 e experimen n w c e co on n ers were quality f l n s 1 11088 in res to 1 gested under similar conditions except for the botih in the ulrligltgached and bleached condit wetting agent and were then bleached with 0.5% 30 a genera p chlorine. v

These objects are accomplished by digesting 1 th abov example the active wetting agent the-crude cotton linters in dilute caustic soda is the sodium salt of the 'half sulfuricacid ester lution containing agents of the type of the sodium of dodecyl alcohol. In place of the dodecyl alsalts of sulfuric acid esters of saturated aliphatic coho] ,11; 1 may u with similar results the 85 alcohols having 6-18 carbon'atoms or of Sodium corresponding sodium salt of the sulfates of ga g' ggtu a d m y c acids having other saturated aliphatic alcohols of 6 tiihla .car 11 a oms. carbon atoms. These alcohols may be et er In the, practice of my invention crude cotton primary or s ondary and may have either 40 linters are digested with 5-10 parts of a l-5% straight or branched carbon chains. Further- 40 (preferably 2%) solution of caustic soda containmore, Tmay use in place f the dodecyl alcohol- 1.118 between and (Preferably to of ExampleIthe so-called "technical lauryl alco- 050% based Onihe dry welght of the linters) of hol which may be obtained by the carboxylic 6 agents t k fr groups cmprismg hydrogenation of an essentially saturated nateither sodium salts of sulfuric acid esters of satuural on such as coconut on palm kernel on 45 rated aliphatic alcohols having carbon atoms or by the hydrogenation of the acids obtained or sodium salts of saturated aliphatic carboxylic by the hydrolysis of these oils. This hydroacids having -6-18 carbon atoms. With either a d t be further treated H class of agents, mixtures of compounds are on pro may I pounds and in general also the emciency f these separate the more .desirable alcohol fractions.

, agents in dilute caustic solutions is greater for alcohol i e i h is p ulafly ehigher molecular weight sub t ot sirable for use in this invention is obtained by gestioni conditions, temperature and pressure, the hydrogenation of coconut 011 and contains 5 etc., may be varied at will depending on the pursubstantially all the alcohols corresponding in of such alcohols boils above about 0., and

contains a mixture of primary and secondary alcohols having both straight and branched carbon chains and consisting predominantly of 8 to 16 carbon atom alcohols.

- Example 11 In another experiment a mixture of thevsodium salts of saturated aliphatic mono-carboxylic acids containing 6-8 carbon. atoms was substitutedfor the sulfate of normal dodecyl alcohol used in Example I with other conditions of digestion and bleaching remaining the same. In this case the rate of wetting out of the linters by the caustic solution was slightly less rapid than noted with the caustic containing the sulfate of normal do,- decyl alcohol, but this rate was still much faster than that obtained in the absence of any wetting agent. As in the case of the first example, the bleached product was superior in color to the control although approximately 15% less bleach was actually consumed than was the case'with the control. 1 r

Instead of the mixture of salts of the 6 to 8 carbon atom acids of Example 11, I may use with similar results sodium salts of other saturated aliphatic monobasic acids within the range of 6- to 18 carbon atoms, including the straight chain acids ranging 'in chain length from caproic acid to stearic acid, that is, from 6 to 18 carbon atoms, also saturated aliphatic monobasic acids ,having branched chains of 6 to 18 carbon atoms. These salts may be used separately but preferably are used in mixtures containing salts of several acids within the specified range. Desirable mixtures of acids for this purpose may be obtained by thehydrolysis of essentially saturated natural oil such as coconut oil.

Satisfactory mixtures of acids for the purpose of this invention may alsobe obtained by the oxidationof those mixtures of alcohols obtained as by-products in the catalytic synthesis of methanol from carbon monoxide and hydrogen. Thus, a mixture of primary saturated aliphatic alcohols containing both straight and branched carbon chains of 8 to 16 carbon atoms and. boiling product obtained in above 160 0.,

methanol synthesis. This alcohol mixture may be oxidized by known methods to a mixture containing the corresponding acids. The oxidation may be effected by the two-step oxidation of alcohol to acid passing through aldehyde, or by the process disclosed in Patent 1,856,263. 1

Instead of digestion under pressure as outlined above, the crude linters may be digested under atmospheric pressure conditions with caustic solutions containing agents of the kind mentioned above. 'Very, high viscosity linters suitable for" conversion to nitrocellulose to be used indynamite manufacture may be produced in this way. The linters so digested are considerably lighter in color andfreer from hull particles than are dynamite linters prepared without the aid of the above mentioned agents.

The addition of one or more of the foregoing agents to a caustic solution to be used for linters digestion results in rapid wetting of the. linters by the caustic so that digestion starts uniformly throughout the whole mass. Unbleached linters purified by means of the process of this invention are, furthermore, of better color, freer of hull particles and other impurities than are linters purified by digestion with caustic soda alone. Bleaching of such linters is easier than normal with an equivalent high white color obtained by the use of less than the normal quantity of bleach, so that under somemonditions 20-25% bleach may be saved in this way.

On conversion to cellulose derivatives, bleached linters caustic digested according to the present invention are found to produce products, i. e., nitrates, acetates, xanthates, etc.,. of superior quality, being freer of haze producing material and of better color, etc., than normal.

As many apparently widely different embodiments of this invention may departing from the spirit and scope thereof, it is to be understood that I do not limit myself to the specific embodiment thereof except as defined in the appended claim.

I claim:--

,A process for purifying cotton linters which comprises digesting the linters under heat and pressure in dilute caustic soda solution containing a sodium salt of a sulfuric acid ester of a saturated aliphatic alcohol containing 6 to 18 carbon atoms.

. ELMER K. BOLTON.

may be eparated from the .by-

be made without 

